Section 56.97-30 - Hydrostatic tests (modifies 137.4)(a)Provision of air vents at high points. Vents must be provided at all high points of the piping subassembly or system in the position in which the test is to be conducted to purge air pockets while the component or system is filling.(b)Test medium and test temperature.(1) Water will be used for a hydrostatic leak test unless another medium is approved by the Commandant.(2) The temperature of the test medium will be that of the available source unless otherwise approved by the Commandant upon review of the metallurgical aspects of the piping materials with respect to its brittle fracture properties.(c)Check of test equipment before applying pressure. The test equipment must be examined before pressure is applied to ensure that it is tight and that all low-pressure filling lines and other items that should not be subjected to the test pressure have been disconnected or isolated by valves or other suitable means.(d)Examination for leakage after application of pressure. Following the application of the hydrostatic test pressure for a minimum of 10 minutes (see paragraph (g) of this section), examination for leakage must be made of all joints, connections and of all regions of high stress, such as regions around openings and thickness-transition sections.(e)Minimum required hydrostatic test pressure. Except as otherwise permitted in paragraph (f) of this section or § 56.97-40 , piping systems must be subjected to a hydrostatic test pressure that at every point in the system is not less than 1.5 times the maximum allowable working pressure.(f)Maximum permissible hydrostatic test pressure.(1) When a system is tested hydrostatically, the test pressure must not exceed the maximum test pressure of any component such as vessels, pumps, or valves in the system.(2) At no time during the hydrostatic test may any part of the piping system be subjected to a stress greater than 90 percent of its yield strength (0.2 percent offset) at test temperature.(g)Hydrostatic test pressure holding time. The hydrostatic test pressure must be maintained for a minimum total time of 10 minutes and for such additional time as may be necessary to conduct the examination for leakage required by paragraph (d) of this section.CGD 73-254, 40 FR 40167, Sept. 2, 1975, as amended by USCG-2003-16630, 73 FR 65185 , Oct. 31, 2008